1. Field of the Invention
The present invention relates to a forced acoustic dipole and a forced acoustic multipole array using the same, and more particularly, to a forced acoustic dipole that is capable of freely steering the direction of an acoustic lobe and a forced acoustic multipole array using the same.
2. Discussion of Related Art
When a conventional speaker system is used to reproduce sound, the sound naturally radiates and can bother other people. In order to minimize the disturbance of others and protect privacy, personal acoustic systems such as headphones, earphones, and so on, are generally used. However, occlusion effect remains as a problem to be solved. Therefore, there is a need to minimize the disturbance of others and solve the problem of the occlusion effect.
One type of personal acoustic system, a line speaker array system, has been proposed to generate a directional lobe using a line speaker array.
The line speaker array system is configured to pass a sound signal through a digital filter, which is adjusted to have directionality, and output the sound signal for listeners to hear at a predetermined position.
However, since the line speaker array system should have filters attached to the speakers, increase in the number of speakers complicates the structure of the system, and spatial resolution of radio frequency is decreased to generate a side-lobe. In addition, since speaker arrangement should be lengthened in proportion to wavelength in order to control low-frequency sound, frequency should be confined to a controllable range for a limited length. In particular, since optimal directional characteristics depend on frequency due to the position of the fixed speakers, numerous filters are needed. In addition, in order to obtain optimal directional characteristics at each frequency, optimal filter coefficients should be calculated one by one.
In order to solve these problems, a speaker system having a simple structure using an acoustic dipole has recently been proposed. However, due to characteristics of the acoustic dipole, the direction of the speaker system's acoustic lobe where sound can be heard cannot be adjusted.